A system for coating fertilizer substrates

ABSTRACT

A system for coating fertilizer substrates is provided. The system comprises a mixing unit wherein the mixing unit comprises a container bowl having an inlet portion and an outlet portion wherein the inlet portion is operatively fastened to a hot air conduit having a blowing unit connected at one end. The invention also relates to a process for coating fertilizer substrates and the coated substrates thereof.

FIELD OF INVENTION

The present invention relates to a system for coating fertilizersubstrates. The invention also relates to a process for coatingfertilizer substrates and the coated substrates thereof.

BACKGROUND

Several devices and methods are conventionally known for coatingfertilizer substrates. Conventionally, coatings are made for controllingthe release of fertilizer and the coatings included resins and waxes.Some of the key challenges involved in coating fertilizer substratesinclude obtaining adequate adherence of the coating over the substrates,ensuring homogeneity of distribution of the coating over the substrate,and preventing agglomeration of particles during the process of coating.Achieving adherence on a solid substrate coated by solid particles ischallenging and uniform adherence of solid particles over the substrateis essential in ensuring homogeneity of the coating. Though adherencepromoters could be employed to solve this problem, practically, in thepresence of such promoters, substrate surfaces tend to agglomerate.Further the device used for coating are required to be kept in anenvironment that does not facilitate degradation of the fertilizersubstrates. There is therefore a need to have a device for coatingfertilizer substrates that solve the above referred problems in the art.

SUMMARY OF INVENTION

The present invention provides a system for coating a fertilizer.

The invention provides a system comprising a mixing unit wherein themixing unit comprises a container bowl having an inlet portion and anoutlet portion wherein the inlet portion is operatively fastened to ahot air conduit having a blowing unit connected at one end.

In one embodiment, the invention provides a system comprising a mixingunit wherein the mixing unit comprises a container bowl having an inletportion and an outlet portion wherein the inlet portion is operativelyfastened to a hot air conduit having a blowing unit connected at oneend, wherein the blowing unit comprises a heating element

In one embodiment, the invention provides a system comprising a mixingunit wherein the mixing unit comprises a container bowl having an inletportion and an outlet portion wherein the inlet portion is operativelyfastened to a hot air conduit having a blowing unit connected at oneend, wherein the mixing unit is adapted to be mounted on a mounting unit

In one embodiment, the invention provides a system comprising a mixingunit wherein the mixing unit comprises a container bowl having an inletportion and an outlet portion wherein the inlet portion is operativelyfastened to a hot air conduit having a blowing unit connected at oneend, wherein the mixing unit is adapted to be mounted on a mounting unitand wherein the mounting unit is adapted to mount a drive motor and agear box In one embodiment, the invention provides a system comprising amixing unit wherein the mixing unit comprises a container bowl having aninlet portion and an outlet portion wherein the inlet portion isoperatively fastened to a hot air conduit having a blowing unitconnected at one end wherein the blowing unit is adapted to provide ahot air blow into the inner volume of the mixing unit.

In one embodiment, the invention provides a system comprising a mixingunit wherein the mixing unit comprises a container bowl having an inletportion and an outlet portion wherein the inlet portion is operativelyfastened to a hot air conduit having a blowing unit connected at one endwherein the system is adapted to first coat a fertilizer substrate witha gel to form a gel-coated substrate and then coat the gel-coatedsubstrate with a powder. In one embodiment, the invention provides asystem comprising a mixing unit wherein the mixing unit comprises acontainer bowl having an inlet portion and an outlet portion wherein theinlet portion is operatively fastened to a hot air conduit having ablowing unit connected at one end wherein the system is adapted to firstcoat a fertilizer substrate with a gel to form a gel-coated substrateand then coat the gel-coated substrate with a powder, wherein the powdercomprises a super absorbent polymer.

In another embodiment the invention provides a process for coating afertilizer, the process comprising charging a mixing unit with afertilizer substrate, first coating the substrate with a gel to form agel-coated substrate then coating the gel-coated substrate with apowder.

In a further embodiment, the invention provides coated particlesprepared by the process of the invention wherein the coated particulatesconsist essentially of a fertilizer substrate and a super absorbentpolymer.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing, which is included to further illustrate anembodiment of the invention and together with the description serve toexplain the principles of the invention. It is meant to be an exemplaryillustration provided to enable persons skilled in the art to practicethe disclosure and is not intended to limit the scope of the appendedclaims.

FIG. 1 displays an exploded view of an embodiment of the system of thepresent invention

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Turning now to FIG. 1, the system according to the present inventioncomprise a mixing unit (1). The mixing unit (1) comprises a containerbowl (2) to coat fertilizer substrates with a superabsorbent polymer aswell as an inlet portion (11) and an outlet portion (12). The mixingunit (1) can have various configurations. In one embodiment, the mixingunit has a container bowl (2) having an oblate spheroidal configuration.The mixing unit is adapted to be mounted on a mounting unit (3). Themixing unit can contain plurality of blades adapted to first ensureintimate mixing of the fertilizer substrates with a gel and then thepowder to ensure intimate mixing of gel coated substrates by the SAPpowder. The blades can have a first leg that is attached to the interiorperiphery of the container bowl and a second leg extending to theinterior volume of the bowl towards the vertical axis of rotation of thebowl. When the mixing unit is mounted on a mounting unit, it is drivenby a drive motor and a gear box (4) mounted on the mounting unit (3) toensure adequate mixing of the contents of the container bowl. The drivemotor is placed at the exterior of the mixing unit in contact with agear system. The drive motor rotates the gear system which in turnrotates the mixing unit. The mixing unit is usually provided with aremovable lid at its mouth that allows charging of fertilizersubstrates, dispensing of a gel and for charging superabsorbent polymer.The gel is usually prepared in a gel preparation unit (13). The gel maybe dispensed to the contained bowl (2) by way of a gel-dispensing unit(14) mounted in a cabinet (15). Typically, the gel dispensing unitcomprise a peristaltic pump. Subsequent to addition of the gel,container bowl is charged with a superabsorbent polymer powder and mixedthoroughly. The blowing unit (5) comprises an air blower (6) and anheating element (7). Air blown from the air blower (6) is heated by theheating element (7) and the hot air is conveyed through a conduit (8)terminating at the inlet portion (11) of the container bowl (2). The hotair blow is made after mixing the superabsorbent polymer powder with thegel-coated fertilizer substrates. Hot air usually exits the containerbowl through an outlet portion (12) of the container bowl (2). Thefertilizer substrates used for coating superabsorbent polymers can havevarious morphologies. Typically, the fertilizer substrates are in theparticulate form.

The invention also provides a process for coating fertilizer. Theprocess of the invention involves first charging the fertilizersubstrates to a container bowl (2), preparing a gel to be dispensed intothe container bowl for intimate mixing with the fertilizer substrates,then charging a superabsorbent polymer powder to the gel-coatedfertilizer substrates. The gel material used in the system and processof the invention can comprise a material suitable to form gel from 1.5to 10% by weight of the fertilizer. Advantageously, a starch basedsuperabsorbent polymer is used as the gel formation material. Mostadvantageously, the gel is used at a concentration of 1.5% to 5% byweight of the fertilizer. Though various materials that form a gel couldbe used, the gel formation material is preferably a polymer, for exampleXanthan gum. Other gel forming material include Rhodopol 23® and variouskinds of starch. The concentration of the gel material is optimized andmaintained in order to provide sufficient adherence of superabsorbentpolymer. In particular, for coating of fertilizer substrates, the gelconcentration is of a sufficient level to allow superabsorbent powdercoating while minimizing the loss of nutrient value, for example,nitrogen availability to crop plants. Keeping the amount of gel lowhelps to avoid the formation of lumps during mixing process of gel.After dispensing the gel and thorough mixing of the gel with thefertiliser, the mixture is treated with a hot air blow from the blowingunit, resulting in a free-flowing coated fertilizer substrates.Typically, the heating element is set at a temperature in the range of70 to 100° C. for heating the air required to provide the hot air blow.The progress of the entire process is monitored to prevent lumping andloss of the fertilizer. The coating process is run as a batch orcontinuous process.

Various fertilizer substrates can be coated using the system and processof the invention. In one embodiment the fertiliser that is coated isUrea. Other fertilizers that can be coated using the system of thepresent invention include, but are not limited to, SSP (Single SuperPhosphate), Diammonium Phosphate (DAP), DSP (Double super phosphate),NPK and the mixtures thereof

Fertilizer particulates is usually uniformly coated with SAP. Thethickness of the gel layer and coating material may be varied as per therequirement, but usually coating of uniform thickness is obtained.

Depending upon the method and quantity used to coat the fertilizersubstrates, the layer of “Super Absorbent Polymer” (SAP) coating may beobtained at various percentages/thicknesses. Typically, for thefertilizer substrates of the invention, the percentage of polymers usedmay be from 0.01 to 10% on weight basis. In most cases, SAP coatedfertilizer substrates contain about 0.01 to 10% of SAP. In many cases,SAP coated fertilizer substrates comprise about 0.1 to 10% of SAP. Mostadvantageously, SAP coated particulate fertilizer comprises about 3% ofSAP, i.e, 100 Kilogram of SAP coated fertilizer contains 3 Kilogram ofSAP.

The system and process of the present invention enables coating offertilizer substrates with a superabsorbent polymer powder uniformly toresult in a free flowing superabsorbent polymer coated fertilizerparticles. The system and process of the present invention ensures thatthe SAP coated fertilizer substrates are coated in such a manner thatnutrient value of the fertilizer is not compromised. The system andprocess of the present invention enables such coating without resultingin lump formation or resulting in agglomeration of individual fertilizerparticles. Further, the process of the present invention usessuperabsorbent polymer itself as the gel formation material obviatingthe need of using a separate gel formation material for holding SAPpowder that is treated over the gel-coated fertilizer.

The invention is further illustrated by way of the followingnon-limiting example

Example

-   -   a) Gel preparation

15 g of starch based superabsorbent polymer was scooped into 1 liter ofdistilled water in a beaker and homogenised thoroughly by a homogenizeruntil a viscous gel, free from lumps, is obtained

-   -   b) Coating of UREA with the gel

50 kg of urea was charged into the container bowl of the mixing unit.1.8 kg of precipitated silica is added to the bowl after this. Gelprepared as in a) above was then dispensed into the container bowl usinga dispensing unit, simultaneously starting agitation of the containerbowl by means of the motor. The mixture was agitated for 30 minutesafter closing the container bowl using a lid.

-   -   c) 3 kg of a starch based superabsorbent polymer was added to        the gel coated fertilizer prepared as in b) above. The container        bowl of the mixing unit was agitated again for about 15 minutes.        After 30 minutes, the blowing unit was started and maintained at        80° C. The hot air blow was provided to the container bowl        through the inlet portion of the container bowl connected to a        hot air conduit. The blow was continued for 15 minutes until a        dry, free flowing granules of urea coated superabsorbent polymer        was obtained

The above description is illustrative only and is not limiting Thepresent invention is defined by the claims that follow and their fullrange of equivalents.

1. A system for coating a fertilizer substrate, the system comprising amixing unit, wherein the mixing unit comprises a container bowl havingan inlet portion and an outlet portion, wherein the inlet portion isoperatively fastened to a hot air conduit having a blowing unitconnected at one end.
 2. The system as claimed in claim 1, wherein thecontainer bowl has an oblate spheroidal configuration.
 3. The system asclaimed in claim 1, wherein the system further comprises a gelpreparation unit.
 4. The system as claimed in claim 1, wherein thesystem Ili comprises a gel dispensing unit.
 5. The system as claimed inclaim 1, wherein the blowing unit comprises a heating element
 6. Thesystem as claimed in claim 1, wherein the mixing unit is adapted to bemounted on a mounting unit
 7. The system as claimed in claim 6, whereinthe mounting unit is adapted to mount a drive motor and a gear box 8.The system as claimed in claim 1, wherein the blowing unit is adapted toprovide a hot air blow into an inner volume of the container bowl. 9.The system as claimed in claim 1, wherein the system is adapted to firstcoat a fertilizer substrate with a gel to form a gel-coated substrate,and subsequently to coat the gel-coated substrate with a powder.
 10. Thesystem as claimed in claim 9, wherein the powder comprises a superabsorbent polymer.
 11. A process for coating a fertilizer, the processcomprising charging a mixing unit with a fertilizer substrate, coatingthe substrate with a gel to form a gel-coated fertilizer substrate, andsubsequently coating the gel-coated fertilizer substrate with asuperabsorbent polymer powder to provide coated fertilizer.
 12. Theprocess as claimed in claim 11, wherein the gel comprises a starch-basedsuperabsorbent polymer.
 13. The process as claimed in claim 11, whereinthe concentration of the gel is in the range of 1.5% to 10% by totalweight of the coated fertilizer.
 14. The process as claimed in claim 11,wherein the concentration of the gel is in the range of 1.5% to 5% bytotal weight of the coated fertilizer.
 15. The process as claimed inclaim 11, wherein the concentration of the superabsorbent polymer is inthe range of 0.1 to 10% by total weight of the coated fertilizer. 16.The process as claimed in claim 11, wherein the fertilizer substrate isselected from the group consisting of urea, single superphosphate anddiammonium phosphate, double superphosphate, and NPK
 17. The process asclaimed in claim 11, wherein the superabsorbent polymer coatedfertilizer substrate is treated with hot air at a temperature in therange of 80 to 1000° C.
 18. A coated fertilizer prepared by the processas claimed in claim
 11. 19. The coated fertilizer as claimed in claim18, wherein the coated fertilizer consist essentially of the fertilizersubstrate, the gel and the super absorbent polymer.